1. Technical Field
This application relates to mobile telecommunications systems in general, having particular application in UMTS (Universal Mobile Telecommunications System) in general, and in particular to an apparatus and method for applying ciphering in universal mobile telecommunications system user equipment and network.
2. Description of the Related Art
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In a typical cellular radio system, mobile user equipment (UE) communicates via a radio access radio network (RAN) to one or more core networks. User equipment (UE) comprises various types of equipment such as mobile telephones (also known as cellular or cell phones), lap tops with wireless communication capability, personal digital assistants (PDAs) etc. These may be portable, hand held, pocket sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
The radio access network covers a geographical area divided into a plurality of cell areas. Each cell area is served by at least one base station, which may be referred to as a Node B. Each cell is identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the UEs within range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
UMTS is a third generation public land mobile telecommunication system. Various standardization bodies are known to publish and set standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) has been known to publish and set standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) has been known to publish and set standards for CDMA (Code Division Multiple Access) based UMTS. Within the scope of a particular standardization body, specific partners publish and set standards in their respective areas.
Consider a wireless mobile device, generally referred to as user equipment (UE), that complies with the 3GPP specifications for the UMTS protocol. The 3GPP 25.331 specification, v.3.15.0, referred to herein as the 25.331 specification, addresses the subject of UMTS RRC (Radio Resource Control) protocol requirements between the UMTS Terrestrial Radio Access Network (UTRAN) and the UE.
In UMTS each radio bearer (including signalling radio bearers) may be configured to apply ciphering to all data as part of the security features of UMTS. Both the UE and the UTRAN store ciphering configurations for applying ciphering. The 25.331 standard states in section 8.6.3.4 that, at any given time, the UE needs to store at most two different ciphering configurations (keyset and algorithm) per Core Network (CN) domain at any given time in total for all radio bearers and three configurations in total for all signalling radio bearers.
The ciphering configurations which are stored are: the current ciphering configuration (the configuration which is currently being applied to the data sent or received on the radio bearer); a new ciphering configuration (if one exists); and an old configuration.
As far as a new ciphering configuration is concerned, if the UTRAN has decided to change the ciphering configuration, there is a period of time after the new configuration has been sent to the UE and before the new configuration is used. This period of time allows the UTRAN and UE radio bearers to synchronise a move to the new configuration at the same time and so no loss of data is encountered. The time at which the new configuration becomes current may be different for each radio bearer as it depends on traffic flow in that radio bearer.
The old configuration is also stored because Packet Data Units (PDUs) which have failed to be received correctly may be retransmitted by the UTRAN and are ciphered using the configuration which was current at the time they were first sent. It is therefore possible that some PDUs which were originally sent before the new ciphering configuration was activated are resent with the previously used (old) ciphering configuration.
Parties may submit proposals to 3GPP and the agenda item TSGR2#((99)K58 submitted to the TSG-RAN working group 2 of the 3GPP (which may be found at <http://www.3gpp.org/ftp/tsg_yan/WG2_RL2/TSGR2—09/Docs/Zips/R2-99k58.doc>) relates to the activation time for new ciphering configurations in Unacknowledged Mode (UM) and Acknowledged Mode (AM).
There are proposed strategies for dealing with ciphering configurations. A number of such strategies are detailed below.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of an apparatus and method for applying ciphering in mobile telecommunications system user equipment.
The same reference numerals are used in different figures to denote similar elements.